This invention relates to energy storage systems, and more particularly to a cold-storing installation of the type having an ice storage reservoir comprising an insulated container filled with water, heat-exchange pipes inserted in the container and forming a first heat exchanger, a refrigeration unit connected to the first heat exchanger and forming a first circuit in which a medium circulates for charging the ice storage reservoir and passes through the heat-exchange pipes, so that the water in the container is transformable into ice, supply means for supplying water to the container, drainage means for withdrawing cooled water from the container for discharging the storage reservoir, and means for circulating the water in the container.
Such cold-storing installations having an ice storage reservoir are utilized particularly in air conditioning and refrigeration plants having a cold demand which is subject, for example, to very great fluctuations within 24 hours. During the night, for instance, there may be a very low cold demand, whereas during the day this demand can be very high. Without the use of such storage reservoirs, the output of such refrigeration plants would have to be designed for this peak load. However, the plants would then be overdimensioned for the major part of their operating time. Unnecessarily high investment and operating costs would thereby occur, the yield being very low.
By using ice storage reservoirs, cold can be produced during the night, for example. This is particularly worthwhile when electric current can then be procured at a reduced rate. During the daytime, the cold demand can then be covered by the storage reservoir, for instance, and peak power loads attributable to refrigeration units are greatly decreased. Such plants can thereby be made smaller, thus leading to better efficiency of the plant and lower operating costs.
Cold-storing installations having an ice storage reservoir have already been proposed. Here the ice storage reservoirs, consisting of an insulated container filled with water, are provided with heat exchangers having suitable heat-exchange pipes. To charge the storage reservoir, a medium cooled in a refrigeration unit is passed through the heat-exchange pipes. This produces in the container growing ice cylinders disposed about the respective heat-exchange pipes. To discharge this storage reservoir, water is supplied to the container from above while the cooled water can be drained at the bottom of the containers. During this operation, water flows around the ice cylinders formed about the heat-exchange pipes, and these cylinders melt.
One drawback of this type of ice-water storage reservoir is that when it is charged, the water in the container must not freeze completely into a block of ice since there must be room for the water to flow through in order that an efficient transfer of heat may take place between the ice cylinders and the water. Consequently, the individual heat-exchange pipes must be sufficiently far apart, resulting in a large space requirement. Furthermore, each discharge must be carried out until the ice is completely melted before charging, i.e., ice formation, can be started again. If complete melting does not take place, the danger exists that through irregular melting and irregular ice formation, large blocks of ice may be formed in the container through which the water no longer flows for discharging, leading to a loss of efficiency. Thus, it is necessary for such ice storage reservoirs to be monitored, which calls for additional personnel. Hence such ice storage reservoirs are more suitable for industrial operations. By means of this ice storage reservoir, however, the advantage is achieved that the water drained off at the time of discharge has a low temperature and that there is good discharge performance.
Ice-storage reservoirs have also been proposed which likewise have a water-filled insulated container in which heat exchangers having heat-exchange pipes are inserted in the same way and through which a medium cooled in a refrigeration unit circulates, so that the water in the container is converted into ice when the storage reservoir is charged. Here cooling can take place until the water is completely frozen and forms a block of ice. Such ice storage reservoirs are discharged in the same way they are charged, via the heat-exchange pipes of the heat exchangers, by passing the medium to be cooled through the heat-exchange pipes, whereupon the cooled medium can then be supplied to a suitable installation. Through the heat transfer, the ice is melted, this taking place initially in the immediate vicinity of the heat-exchange pipes. Such ice storage reservoirs have the advantage of very compact construction since the heat-exchange pipes can be disposed relatively close to one another. Operational reliability is very high; it is not necessary to carry out the discharge until the ice has completely melted into water; charging can take place again at any time. Such ice storage reservoirs are not so efficient as those described before since a space filled with water is produced between the heat-exchange pipes and the surrounding ice quite soon after the discharge operation, whereby the efficiency of the heat transfer is restricted.
It is an object of this invention to provide a cold-storing installation having an ice storage reservoir which is so designed that high efficiency is achieved.
Another object of the invention is to provide such a cold-storing installation wherein the ice storage reservoir can be charged at any time without complete discharge having to take place beforehand.
A further object of the invention is to provide a cold-storing installation wherein the cooled medium made available has a low temperature.
Still another object of the invention is to provide such an installation requiring no monitoring personnel.